Toothbrush brushhead for a power toothbrush with angled bristles

ABSTRACT

The brushhead, which has a rotating action, includes a bristle plate and three separate sets of bristle tufts. A first set of bristle tufts extends longitudinally down the approximate center of the brushhead and is arranged to extend vertically from the base plate. The second and third sets of bristle tufts are arranged on opposing sides of the first set of bristle tufts, with the second and third sets of bristle tufts being arranged at an angle outwardly, in opposing directions, from the first set of bristle tufts, the angle being in the range of 5°-45°. The length of all the bristle tufts is established so that the tips of the bristles in the first, second and third sets of bristle tufts form a shallow arc.

This invention relates generally to brushheads for toothbrushes, and more specifically concerns a brushhead with a particular bristle arrangement on the brushhead.

Certain power toothbrushes, for example, sonic (acoustic) energy toothbrushes such as shown and described in U.S. Pat. No. 5,378,153, which is owned by the assignee of the present invention, provide a selected amount of acoustic energy to the teeth for cleaning, by bristle-fluid interaction, in addition to scrubbing action by the tips of the bristles being in direct physical contact with the teeth. The acoustic energy provided to the teeth is particularly effective in cleaning hard-to-reach places, such as between the teeth and into the gingival areas. Acoustic energy thus is desirable for overall effective teeth cleaning. Increasing the applied acoustic energy, which increases the cleaning effect, can be accomplished in one way by increasing the speed of the bristles. However, there are significant limitations on increasing bristle speed, because as bristle speed increases, so does discomfort to the user and also abrasion of the teeth and/or the gums.

It is thus desirable to increase the bristle speed, in order to increase acoustic energy cleaning, without correspondingly increasing the discomfort to the user or abrasion to the teeth and/or gums. This is accomplished by the particular bristle arrangements shown and described herein.

Accordingly, the present invention comprises a brushhead for a power toothbrush in which the brushhead is driven in a side-to-side motion, comprising: a brushhead base plate; a plurality of lateral rows of bristle tufts, each row comprising: a first set of bristle tufts set into the base plate substantially vertically; a second set of bristle tufts set into the base plate extending along one side of the first set of bristle tufts and angled outwardly therefrom at an angle within the range of 5°-15°; and a third set of bristle tufts set into the base plate extending along the opposing side of the first set of bristle tufts and angled outwardly therefrom within the range of 5°-15°, wherein the bristle tufts in the second and third sets are set into the base plate a horizontal distance “r” in the range of 1.2 mm to 4 mm from the center of rotation of the brushhead.

FIGS. 1A and 1B show a bristle arrangement where the center line of the bristles is located a distance from the center of motion of a rotating brushhead.

FIGS. 2A and 2B show an angled bristle arrangement where the center line of the bristles passes through the center of rotation of a rotating brushhead.

FIG. 3 shows a brushhead arrangement of the present invention.

FIG. 4 shows a power toothbrush which could use the bristle arrangement of FIG. 3.

FIG. 5 is a graph of bristle effectiveness involving bristle mounting angle and the bristle distance from the center of the brushhead.

FIG. 6 is a cross-section showing a bristle plate and a bristle mounted in a particular angular orientation on the bristle plate which incorporates a future of the present invention.

FIG. 7 is a cross-section showing a bristle plate with another bristle arrangement.

FIG. 8 is a graph of bristle effectiveness involving change in the bristle “action” length against the difference between the “action” angle and the “bristle” angle.

FIG. 4 shows a power toothbrush which could use the bristle arrangement of the present invention. The power toothbrush 10 includes a handle portion 12 and a head portion 14. Head portion 14 includes an extending brushhead arm 16, at the remote end of which brushhead 18 is mounted. Arm 16, in operation, is rotated through an arc of selected amplitude by a drive system located in the handle. The drive system is not shown in detail. The drive system may be any one of various arrangements, including a motor with a rotating armature or an electromagnetic driver, such as shown in the '153 patent. It should be understood that the present invention is not limited to a particular drive system.

FIGS. 1A and 1B show a conventional bristle arrangement, including a bristle plate 23, where the bristles (one bristle tuft 25 is shown for illustration) are located a distance “r” from the center of rotation of the brushhead. Each bristle tuft includes a number of individual bristles, typically between 10 and 50. In this arrangement, a large force is generated by the tops of the bristles in the bristle tufts on the teeth surface 26, due to compression of the bristle during operation.

FIGS. 2A and 2B show another conventional bristle arrangement, including a bristle plate 27, in which the bristles (one bristle tuft 28 is shown) are angled, extending from in effect the center of rotation 29 of the brushhead (bristle plate). In this arrangement, there is no compressive loading by the bristle tips on the teeth and hence little, if any, scrubbing action on the teeth.

FIG. 3 shows the brushhead configuration of the present invention. The brushhead 30 includes a bristle plate 32, which can have various configurations, with a plurality of bristle tufts shown mounted therein. In the embodiment shown, the plurality of bristles includes three sets of bristle tufts (38, 40, and 42), at one longitudinal location along the bristle plate. The first set shows two bristle tufts, off the center line of the bristle plate, while the second and third sets include only one tuft. The term “set” herein includes one tuft. There could, however, be more than one tuft in each set. In one brushhead embodiment, comprising a plurality of lateral rows of bristle tufts, each row includes one bristle tuft in the second and third sets of bristle tufts and between zero and two bristle tufts in the first set of bristle tufts. The rows with zero tufts in the first set will be in the first rows and the last one/two rows. Other brush configurations are of course possible.

The first set of bristle tufts 40 (two tufts are shown) extend vertically upwards from bristle plate 32, approximately 1.2 cm. high. Each bristle tuft contains approximately 10-50 bristles. Typically, the bristles will be made of nylon, and will be in the range of 0.004-0.009 inches in diameter.

The second and third sets of bristle tufts (38 and 42, with one tuft shown in each set) are located on opposite sides of the first, mid-position bristle tuft set 40. The second and third sets of bristle tufts are substantially identical to each other and are similar to the bristles in the first set, being also made of nylon and having approximately the same diameter as the first set. The second and third sets of bristle tufts, however, are oriented at an angle to the vertical, as shown in FIG. 3. In the embodiment shown, this angle is in the range of 5°-15°, preferably 10°. The angle from the vertical for the bristle tuft sets is the same for both the second and third sets of bristle tufts, except in opposing directions.

The length of the bristles in the second and third sets of bristles is such that when the brushhead is at rest, as shown in FIG. 3, the tips of all the bristles (the bristles in first, second and third sets of bristle tufts) form a shallow arc, with the center of the arc being the center of motion of the bristle tufts.

FIG. 5 shows a graph of bristle angle versus radius of movement action, providing a region of effective action of the toothbrush. The range of effectiveness for “r” (distance from center of brushhead) is 1.2 mm to 4 mm, while the range of effectiveness for bristle angle is between 0°-8° for an r of 1.2 mm and between 5°-50° for an r of 4 mm. Within the rectangle 60, defined by the above limits, brushing experience is good.

FIG. 6 shows another bristle arrangement, including a bristle plate 61 in which a bristle tuft 62 is mounted at point 64, angled from the center of rotation 66 of the brushhead, and having both what is referred to herein as an “action angle” (the angle “BAC”), where the line “CE” is perpendicular to the longitudinal axis of the bristle plate and extends through the bristle plate center of rotation A, and a “bristle mounting angle” (the angle “BEC”), where the line BE extends through the mounting point D of the bristle tuft on the bristle plate.

The angular difference between the action angle and the bristle angle (the “delta” angle ABE) has a direct and significant influence on the performance of the toothbrush. In a normal bristle configuration there is the potential for the bristles to bend and/or be dragged across a tooth surface, as opposed to a “dig” and/or “buckle” action against the surface. The most efficiently performing bristle arrangement will have a hypothetical delta angle of 0°; it has been established in this present invention that the upper limit of an efficiently performing bristle arrangement is with a delta angle of 21°. A practical and preferred range for the delta angle is 17-21°.

FIG. 7 shows another bristle arrangement, including a bristle plate 70, in which two adjacent bristle tufts 72, 74 are angled from the center of rotation A of the brushhead (bristle plate 70). FIG. 7 illustrates “action lengths” of bristle tufts 72 and 74, action lengths being the distance between the respective tips of the bristle tufts 72 and 74 and the axis of rotation

A of the bristle plate.

Considering adjacent tufts of bristles (as viewed in the plane perpendicular to the axis of rotation), such as bristle tufts 72 and 74, as the bristles move against the teeth, differences in action length between two adjacent tufts have to be accommodated as the longer tuft comes into position by flexing of tufts or moving of the brush by the user (or in reaction to the impact of the longer action length tuft in a space previously accommodating the smaller one). The flexing or impact will be detrimental to the experience of the user as well as brush performance (energy is wasted). The most efficiently performing brush will have a zero change in action length from adjacent tuft to adjacent tuft. It has been established by the inventors herein that the most efficiently performing toothbrush will have an upper limit of 1.25 mm in the change of action length from bristle tuft to adjacent bristle tuft.

FIG. 8 is a graph of change in action length between adjacent tufts versus the angular difference (delta angle) between the action angle and the bristle angle discussed above relative to the arrangement of FIG. 6. As noted above, the range of effectiveness for the change in action length is 0 mm to 1.25 mm, while the range of effectiveness of the delta angle is 0° to 21°. These two ranges produce a rectangular region 80, where brushing experience is good.

The angled bristle arrangement has an important cleansing effect during operation of the toothbrush. It provides users an enhanced brushing experience. The amplitude of the brush motion, as well as the frequency of the motion, can be increased, to increase the speed of the bristles, which improves cleaning, without causing discomfort to the user or abrasion to the user's mouth/gum tissues. The end loading of the bristles which causes the discomfort is a function of the impact angle created by the angled bristles. When the bristles are angled away from the direction of motion, but offset from the center of rotation of the brushhead, the end loading of the bristle tips is decreased to some extent, resulting in weaker forces to the teeth. This weaker loading provides less mechanical cleaning action on the teeth, but does decrease the acoustic energy transfer to the teeth.

The acoustic energy transfer can now be increased by increasing the speed and/or amplitude of the bristle motion, without discomfort, which is caused by the mechanical scrubbing action. As an example, the amplitude of the brush movement can be increased from approximately 13° to 16°, an increase in the range of 15-30 percent. At the same time; or independently, the speed of the brushhead can be increased, by approximately 15-30 percent. Both the amplitude and speed of the brushhead can be increased if desired.

Hence, a new bristle arrangement has been disclosed, using a radially angled bristle arrangement, which permits an increase of velocity or amplitude of the rotational brushhead (with bristles) motion, which in turn results in enhanced cleaning, without discomfort and/or abrasion to the tissues.

Although a preferred embodiment of the invention has been disclosed for purpose of illustration, it should be understood that various changes, modifications and substitutions can be incorporated in the embodiment without departing from the spirit of the invention which is defined by the claims which follow: 

1. A brushhead for a power toothbrush in which the brushhead is driven in a side-to-side motion, comprising: a brushhead base plate; a plurality of lateral rows of bristle tufts, each row comprising: a first set of bristle tufts set into the base plate substantially vertically; a second set of bristle tufts set into the base plate extending along one side of the first set of bristle tufts and angled outwardly therefrom at an angle within the range of 5°-15°; and a third set of bristle tufts set into the base plate extending along the opposing side of the first set of bristle tufts and angled outwardly therefrom within the range of 5°-15°, wherein the bristle tufts in the second and third sets are set into the base plate a horizontal distance “r” in the range of 1.2 mm to 4 mm from the center of rotation of the brushhead.
 2. The bristle configuration of claim 1, wherein the angle of the bristles is approximately 10°.
 3. The bristle configuration of claim 1, wherein the length of the bristles in the first, second and third sets of bristles is such that the tips of the bristles from a shallow arc centered on the axis of rotation of the brushhead base plate.
 4. A brushhead for a power toothbrush in which the brushhead is driven in a side-to-side motion, comprising: a brushhead base plate; a plurality of lateral rows of bristle tufts, each row comprising: a first set of bristle tufts set into the base plate substantially vertically, arranged in the longitudinal direction of the base plate; a second set of bristle tufts set into the base plate extending along one side of the first set of bristle tufts and angled outwardly therefrom; and a third set of bristle tufts set into the base plate extending along the opposing side of the first set of bristle tufts and angled outwardly therefrom, wherein there is a difference in length between the bristles in adjacent tufts of bristle in the second and third sets of bristles in the range of 0-1.25 mm and an angular difference between the action angle and the bristle angle of the bristle tufts in the range of 0°-21°.
 5. The brushhead of claim 4, wherein the second and third sets of bristle tufts are arranged on the bristle plate to be offset from the center of rotation of the bristle plate.
 6. The brushhead of claim 4, wherein the amplitude of movement of the brushhead and the speed of the brushhead can be increased by approximately 15-30 percent without increasing discomfort to the users.
 7. The brushhead of claim 4, wherein the angular difference is within the range of 17°-21°. 